1. Field of the Disclosure
This disclosure relates generally to production of hydrocarbons from wells using electrical submersible pumps.
2. Brief Description of the Related Art
Oil wells (wellbores) are drilled to a selected depth in earth formations for the production of hydrocarbons. Such wells are often cased after drilling with a metallic casing. A production string containing a variety of devices is placed inside the casing to flow fluid from the formations to the surface. Formation fluid often includes oil, gas and water. Oil is separated from water and gas at the surface and transported for processing. The production string includes a variety of device, such as zone isolation devices, such as packers, sand control devices for controlling flow of solid particles from the formation into the production tubing, and flow control device, such as valves that control the flow of the formation fluid into the wellbore, The fluid in the tubing flows to a surface separator, where oil is separated from gas and water. The formation fluid typically flows naturally into the production tubing because the pressure of the formation is greater than the pressure in the tubing. In the early phases of oil wells, the differential pressure between the formation and the production tubing is sufficient to cause the fluid in the tubing to reach the surface. In the later phases of some wells, this pressure differential is not sufficient to cause the fluid in the tubing to flow to the surface. In some such cases an artificial lift mechanism in the wellbore is used to pump the fluid in the production tubing to the surface. A common lifting mechanism used is an electrical submersible pump (“ESP”). An ESP is installed in the wellbore to draw or lift the liquid fluid from the wellbore into the production tubing. The ESP is designed to remain submerged in a liquid during operation. A selected level of the liquid (oil and/or water) above the ESP is desired for optimal ESP use.
The disclosure herein provides a system for controlling the liquid level (or “head”) above the ESP in real or substantially real time and for controlling the operation of the ESP.